This invention relates to an improved marking head for use in an electrochemical marking process for imaging conductive metal parts.
In most electrochemical marking processes, a grounded receiving surface is marked or imaged by firing a block-like electrode through a stencil in the presence of a suitable electrolyte. The electrical current passing through the stencil is shaped in accordance with the design cut therein, whereby a latent image of the stencil pattern is recorded upon the receiving surface. Under the combined influence of the electrical charge and the electrolyte an etch is formed upon the receiving surface in conformity with the image pattern and, at the same time, an oxide of the base material is deposited within the etched region to create a dark and clearly discernible mark. Because the electrochemical marking process does not deform or otherwise harm the surface of the receiving part, and because the marking equipment is also clean and easy to operate, this type of imaging process has found widespread use in industry.
It is now the common practice to change stencils every time a part number changes or different information is to be recorded on the receiving part. The cutting of new stancils and replacing them in the marking apparatus is generally a time-consuming and costly procedure. By the same token, when a large number of stencils are to be handled in some type of ordered sequence, the danger of an error occurring is greatly increased. Because the subject marking process creates a permanent mark, mismarked parts ordinarily must be scrapped or extensively reworked in order to render them reusable. In any event, erroneous marking of the parts typically proves to be an expensive proposition for the manufacturer.